Aerodynamic Losses of a Cambered Turbine Vane: Influences of Surface Roughness and Freestream Turbulence Intensity

The effects of surface roughness and freestream turbulence level on the aerodynamic performance of a turbine vane are experimentally investigated. Wake profiles are measured with three different freestream turbulence intensity levels (1.1%, 5.4% and 7.7%) at two different locations downstream of the test vane trailing edge (one and 0.25 axial chord lengths). Chord Reynolds number based on exit flow conditions is 0.9 × 106. The Mach number distribution and the test vane configuration both match arrangements employed in an industrial application. Four cambered vanes with different surface roughness levels are employed in this study. Effects of surface roughness on the vane pressure side on the profile losses are relatively small compared with suction side roughness. Overall effects of turbulence on local wake deficits of total pressure, Mach number, and kinetic energy are almost negligible in most parts of the wake produced by the smooth test vane, except that higher freestream losses are present at higher turbulence intensity levels. Profiles produced by test vanes with rough surfaces show apparent lower peak values in the center of the wake. Integrated Aerodynamic Losses (IAL) and area-averaged loss coefficient YA are also presented and compared with results from other research groups.

Aerodynamic Losses of a Cambered Turbine Vane: Influences of Surface Roughness and Freestream Turbulence Intensity

10.1115/1.2185125 ◽

2006 ◽

Vol 128 (3) ◽

pp. 536-546 ◽

Cited By ~ 18

Author(s):

Qiang Zhang ◽

Phillip M. Ligrani

Keyword(s):

Surface Roughness ◽

Mach Number ◽

Turbulence Intensity ◽

Suction Side ◽

Freestream Turbulence ◽

Smooth Test ◽

Profile Losses ◽

Turbine Vane ◽

Mach Number Distribution ◽

The effects of surface roughness and freestream turbulence level on the aerodynamic performance of a turbine vane are experimentally investigated. Wake profiles are measured with three different freestream turbulence intensity levels (1.1%, 5.4%, and 7.7%) at two different locations downstream of the test vane trailing edge (1 and 0.25 axial chord lengths). Chord Reynolds number based on exit flow conditions is 0.9×106. The Mach number distribution and the test vane configuration both match arrangements employed in an industrial application. Four combered vanes with different surface roughness levels are employed in this study. Effects of surface roughness on the vane pressure side on the profile losses are relatively small compared to suction side roughness. Overall effects of turbulence on local wake deficits of total pressure, Mach number, and kinetic energy are almost negligible in most parts of the wake produced by the smooth test vane, except that higher freestream losses are present at higher turbulence intensity levels. Profiles produced by test vanes with rough surfaces show apparent lower peak values in the center of the wake. Integrated aerodynamic losses and area-averaged loss coefficient YA are also presented and compared to results from other research groups.

Second Law Analysis of Aerodynamic Losses: Results for a Cambered Vane With and Without Film Cooling

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2012-70021 ◽

2012 ◽

Author(s):

Phil Ligrani ◽

Jae Sik Jin

Keyword(s):

Surface Roughness ◽

Mach Number ◽

Turbulence Intensity ◽

Film Cooling ◽

Chord Length ◽

Second Law ◽

Exergy Destruction ◽

Freestream Turbulence ◽

Second Law Analysis ◽

Results of second law analysis of experimentally-measured aerodynamic losses are presented for a cambered vane with and without film cooling, including comparisons with similar results from a symmetric airfoil. Included are distributions of local entropy creation, as well as mass-averaged magnitudes of global exergy destruction. The axial chord length of the cambered vane is 4.85 cm, the true chord length is 7.27 cm, and the effective pitch is 6.35 cm. Data are presented for three airfoil Mex distributions (including one wherein the flow is transonic), magnitudes of inlet turbulence intensity from 1.1 percent to 8.2 percent, and ks/cx surface roughness values of 0, 0.00108, and 0.00258. The associated second law aerodynamics losses are presented for two different measurement locations downstream of the vane trailing edge (one axial chord length and 0.25 axial chord length). The surface roughness, when present, simulates characteristics of the actual roughness which develops on operating turbine airfoils from a utility power engine, over long operating times, due to particulate deposition and to spallation of thermal barrier coatings (TBCs). Quantitative surface roughness characteristics which are matched include equivalent sandgrain roughness size, as well as the irregularity, non-uniformity, and the three-dimensional irregular arrangement of the roughness. Relative to a smooth, symmetric airfoil with no film cooling at low Mach number and low freestream turbulence intensity, overall, the largest increases in exergy destruction occur with increasing Mach number, and increasing surface roughness. Important variations are also observed as airfoil camber changes. Progressively smaller mass-averaged exergy destruction increases are then observed with changes of freestream turbulence intensity, and different film cooling conditions. In addition, the dependences of overall exergy destruction magnitudes on mainstream turbulence intensity and freestream Mach number are vastly different as level of vane surface roughness changes. When film cooling is present, overall mass-averaged exergy destruction magnitudes are significantly less than values associated with increased airfoil surface roughness for both the cambered vane and the symmetric airfoil. Exergy destruction values (associated with wake aerodynamic losses) for the symmetric airfoil with film cooling are then significantly higher than data from the cambered vane with film cooling, when compared at a particular blowing ratio.

Second Law Analysis of Aerodynamic Losses: Results for a Cambered Vane With and Without Film Cooling

10.1115/1.4007588 ◽

2013 ◽

Vol 135 (4) ◽

Cited By ~ 1

Author(s):

Phil Ligrani ◽

Jae Sik Jin

Keyword(s):

Surface Roughness ◽

Mach Number ◽

Turbulence Intensity ◽

Film Cooling ◽

Chord Length ◽

Second Law ◽

Exergy Destruction ◽

Freestream Turbulence ◽

Second Law Analysis ◽

Results of second law analysis of experimentally-measured aerodynamic losses are presented for a cambered vane with and without film cooling, including comparisons with similar results from a symmetric airfoil. Included are distributions of local entropy creation, as well as mass-averaged magnitudes of global exergy destruction. The axial chord length of the cambered vane is 4.85 cm, the true chord length is 7.27 cm, and the effective pitch is 6.35 cm. Data are presented for three airfoil Mex distributions (including one wherein the flow is transonic), magnitudes of inlet turbulence intensity from 1.1% to 8.2%, and ks/cx surface roughness values of 0, 0.00108, and 0.00258. The associated second law aerodynamics losses are presented for two different measurement locations downstream of the vane trailing edge (one axial chord length and 0.25 axial chord length). The surface roughness, when present, simulates characteristics of the actual roughness which develops on operating turbine airfoils from a utility power engine, over long operating times, due to particulate deposition and to spallation of thermal barrier coatings. Quantitative surface roughness characteristics which are matched include equivalent sandgrain roughness size, as well as the irregularity, nonuniformity, and the three-dimensional irregular arrangement of the roughness. Relative to a smooth, symmetric airfoil with no film cooling at low Mach number and low freestream turbulence intensity, overall, the largest increases in exergy destruction occur with increasing Mach number, and increasing surface roughness. Important variations are also observed as airfoil camber changes. Progressively smaller mass-averaged exergy destruction increases are then observed with changes of freestream turbulence intensity, and different film cooling conditions. In addition, the dependences of overall exergy destruction magnitudes on mainstream turbulence intensity and freestream Mach number are vastly different as level of vane surface roughness changes. When film cooling is present, overall mass-averaged exergy destruction magnitudes are significantly less than values associated with increased airfoil surface roughness for both the cambered vane and the symmetric airfoil. Dimensional exergy destruction values (associated with wake aerodynamic losses) for the symmetric airfoil with film cooling are then significantly higher than data from the cambered vane with film cooling, when compared at a particular blowing ratio.

Mach Number and Freestream Turbulence Effects on Turbine Vane Aerodynamic Losses

Journal of Propulsion and Power ◽

10.2514/1.14837 ◽

2005 ◽

Vol 21 (6) ◽

pp. 988-996 ◽

Cited By ~ 7

Author(s):

Qiang Zhang ◽

Donald Sandberg ◽

Phillip M. Ligrani

Keyword(s):

Mach Number ◽

Freestream Turbulence ◽

Turbine Vane ◽

Turbulence Effects ◽

Influence of Surface Roughness on the Aerodynamic Losses of a Turbine Vane

Journal of Fluids Engineering ◽

10.1115/1.2175163 ◽

2005 ◽

Vol 128 (3) ◽

pp. 568-578 ◽

Cited By ~ 12

Author(s):

Qiang Zhang ◽

Matt Goodro ◽

Phillip M. Ligrani ◽

Ricardo Trindade ◽

Sri Sreekanth

Keyword(s):

Surface Roughness ◽

Mach Number ◽

Kinetic Energy ◽

Three Dimensional ◽

Aerodynamic Loss ◽

Variable Surface ◽

Turbine Vanes ◽

Turbine Vane ◽

Loss Coefficients ◽

The effects of surface roughness on the aerodynamic performance of a turbine vane are investigated for three Mach number distributions, one of which results in transonic flow. Four turbine vanes, each with the same shape and exterior dimensions, are employed with different rough surfaces. The nonuniform, irregular, three-dimensional roughness on the tested vanes is employed to match the roughness which exists on operating turbine vanes subject to extended operating times with significant particulate deposition on the surfaces. Wake profiles are measured for two different positions downstream the vane trailing edge. The contributions of varying surface roughness to aerodynamic losses, Mach number profiles, normalized kinetic energy profiles, Integrated Aerodynamics Losses (IAL), area-averaged loss coefficients, and mass-averaged loss coefficients are quantified. Total pressure losses, Mach number deficits, and deficits of kinetic energy all increase at each profile location within the wake as the size of equivalent sandgrain roughness increases, provided the roughness on the surfaces is uniform. Corresponding Integrated Aerodynamic Loss IAL magnitudes increase either as Mach numbers along the airfoil are higher, or as the size of surface roughness increases. Data are also provided which illustrate the larger loss magnitudes which are present with flow turning and cambered airfoils, than with symmetric airfoils. Also described are wake broadening, profile asymmetry, and effects of increased turbulent diffusion, variable surface roughness, and streamwise development.

Influence of Surface Roughness on the Aerodynamic Losses of a Turbine Vane

Volume 6: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68832 ◽

2005 ◽

Cited By ~ 2

Author(s):

Qiang Zhang ◽

Matt Goodro ◽

Phillip M. Ligrani ◽

Ricardo Trindade ◽

Sri Sreekanth

Keyword(s):

Surface Roughness ◽

Mach Number ◽

Kinetic Energy ◽

Three Dimensional ◽

Aerodynamic Loss ◽

Variable Surface ◽

Turbine Vanes ◽

Turbine Vane ◽

Loss Coefficients ◽

The effects of surface roughness on the aerodynamic performance of a turbine vane are investigated for three Mach number distributions, one of which results in transonic flow and matches an arrangement employed in an industrial application. Four turbine vanes, each with the same shape and exterior dimensions, are employed with different rough surfaces. The non-uniform, irregular, three-dimensional roughness on the tested vanes is employed to match the roughness which exists on operating turbine vanes subject to extended operating times with significant particulate deposition on the surfaces. Wake profiles are measured for two different positions downstream the vane trailing edge. The contributions of varying surface roughness to aerodynamic losses, Mach number profiles, normalized kinetic energy profiles, Integrated Aerodynamics Losses (IAL), area-averaged loss coefficients, and mass-averaged loss coefficients are quantified. Total pressure losses, Mach number deficits, and deficits of kinetic energy all increase at each profile location within the wake as the size of equivalent sandgrain roughness increases, provided the roughness on the surfaces is uniform. Corresponding Integrated Aerodynamic Loss IAL magnitudes increase either as Mach numbers along the airfoil are higher, or as the size of surface roughness increases. Data are also provided which illustrate the larger loss magnitudes which are present with flow turning and cambered airfoils, than with symmetric airfoils. Also described are wake broadening, profile asymmetry, and effects of increased turbulent diffusion, variable surface roughness, and streamwise development.

Effect of Discrete Surface Disturbances on Vane External Heat Transfer

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/97-gt-134 ◽

1997 ◽

Cited By ~ 3

Author(s):

R. S. Bunker

Keyword(s):

Heat Transfer ◽

Turbulence Intensity ◽

Pressure Ratio ◽

Leading Edge ◽

Suction Side ◽

External Heat ◽

Freestream Turbulence ◽

External Heat Transfer ◽

Enhancement Factors ◽

Surface Disturbances

A transonic linear vane cascade has been utilized to assess the effects of localized surface disturbances on airfoil external heat transfer coefficient distributions, such as those which may be created by the spallation of thermal barrier coatings. The cascade operates at an overall pressure ratio of 1.86, with an inlet total pressure of about 5 atm. Cascade Reynolds numbers based on axial chord length and exit velocity range from 2.2 to 4.8 · 106. Surface disturbances are modeled with the use of narrow trip strips glued onto the surface at selected locations, such that sharp forward facing steps are presented to the boundary layer. Surface locations investigated include the near leading edge region on either side of the stagnation point, the midchord region of the pressure side, and the high curvature region of the suction side. Heat transfer enhancement factors are obtained for disturbances with engine representative height-to-momentum thickness ratios, as a function of Reynolds number. Enhancement factors are compared for both smooth and rough airfoil surfaces with added disturbances, as well as low and high freestream turbulence intensity. Results show that leading edge heat transfer is dominated by freestream turbulence intensity effects, such that enhancements of nearly 50% at low turbulence levels are reduced to about 10% at elevated turbulence levels. Both pressure and suction side enhancement factors are dominated by surface roughness caused effects, with large enhancements for smooth surfaces being drastically reduced for roughened surfaces.

Steady Vortex-Generator Jet Flow Control on a Highly Loaded Transonic Low-Pressure Turbine Cascade: Effects of Compressibility and Roughness

10.1115/1.4028214 ◽

2014 ◽

Vol 136 (11) ◽

Cited By ~ 6

Author(s):

Chiara Bernardini ◽

Stuart I. Benton ◽

John D. Lee ◽

Jeffrey P. Bons ◽

Jen-Ping Chen ◽

...

Keyword(s):

Surface Roughness ◽

Mach Number ◽

Flow Control ◽

High Speed ◽

Vortex Generator ◽

Control Performance ◽

Low Pressure Turbine ◽

Blowing Ratio ◽

Turbulent Separation ◽

Mach Number Distribution

A new high-speed linear cascade has been developed for low-pressure turbine (LPT) studies at The Ohio State University. A compressible LPT profile is tested in the facility and its baseline performance at different operating conditions is assessed by means of isentropic Mach number distribution and wake total pressure losses. Active flow control is implemented through a spanwise row of vortex-generator jets (VGJs) located at 60% chord on the suction surface. The purpose of the study is to document the effectiveness of VGJ flow control in high-speed compressible flow. The effect on shock-induced separation is assessed by Mach number distribution, wake loss surveys and shadowgraph. Pressure sensitive paint (PSP) is applied to understand the three dimensional flow and shock pattern developing from the interaction of the skewed jets and the main flow. Data show that with increasing blowing ratio, the losses are first decreased due to separation reduction, but losses connected to compressibility effects become stronger due to increased passage shock strength and jet orifice choking; therefore, the optimum blowing ratio is a tradeoff between these counteracting effects. The effect of added surface roughness on the uncontrolled flow and on flow control behavior is also investigated. At lower Mach number, turbulent separation develops on the rough surface and a different flow control performance is observed. Steady VGJs appear to have control authority even on a turbulent separation but higher blowing ratios are required compared to incompressible flow experiments reported elsewhere. Overall, the results show a high sensitivity of steady VGJs control performance and optimum blowing ratio to compressibility and surface roughness.

Effects of Obstructions and Surface Roughness on Film Cooling Effectiveness With and Without a Transverse Trench

10.1115/1.2950063 ◽

2008 ◽

Vol 131 (1) ◽

Cited By ~ 5

Author(s):

Ruwan P. Somawardhana ◽

David G. Bogard

Keyword(s):

Surface Roughness ◽

Film Cooling ◽

Suction Side ◽

Cooling Effectiveness ◽

Cooling Performance ◽

Film Cooling Effectiveness ◽

Surface Conditions ◽

Turbine Vane ◽

Cylindrical Holes ◽

Better Than

Recent studies have shown that film cooling with holes embedded in a shallow trench significantly improves cooling performance. In this study, the performance of shallow trench configurations was investigated for simulated deteriorated surface conditions, i.e., increased surface roughness and near-hole obstructions. Experiments were conducted on the suction side of a scaled-up simulated turbine vane. Results from the study indicated that as much as 50% degradation occurred with upstream obstructions, but downstream obstructions actually enhanced film cooling effectiveness. However, the transverse trench configuration performed significantly better than the traditional cylindrical holes, both with and without obstructions and almost eliminated the effects of both surface roughness and obstructions.

Effect of Surface Roughness on Conjugate Heat Transfer of a Turbine Vane

Volume 5A: Heat Transfer ◽

10.1115/gt2016-56744 ◽

2016 ◽

Cited By ~ 1

Author(s):

Hongyang Li ◽

Yun Zheng

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Surface Roughness ◽

Suction Side ◽

Transition Process ◽

Considerable Effect ◽

Boundary Layer Transition ◽

Layer Transition ◽

Turbine Vane ◽

Effect Of Surface

For the purpose of researching the effect of surface roughness on boundary layer transition and heat transfer of turbine blade, a roughness modification approach for γ-Reθ transition model was proposed based on an in-house CFD code. Taking surface roughness effect into consideration, No. 5411 working condition of Mark II turbine vane was simulated and the results were analyzed in detail. Main conclusions are as follows: Surface roughness has little effect on heat transfer of laminar boundary layer, while has considerable effect on turbulent boundary layer. Compared with smooth surface, equivalent sand roughness of 100μm increases the temperature for about 28.4K on suction side, reaching an increase of 5%. Under low roughness degree, effect of shock wave dominants on boundary layer transition process on suction side, while above the critical degree, effect of surface roughness could abruptly change the transition point.